[Dual Shade] Match surface and scrim colors with the SurfaceEffects spec

Fix: 404732145
Fix: 404484235
Test: Existing unit tests still pass.
Test: Manually by opening and closing the notifications shade and quick
 settings shade and observing that the colors look as intended, in both
 light and dark mode, with notifications blur on and off.
Flag: com.android.systemui.scene_container
Change-Id: I55854205743dfde2ea95d345d89d9812b85064aa